Method for Avoiding Ribbon Windings

ABSTRACT

A method for avoiding ribbon windings in producing cross-wound bobbins at the workstations of textile machines in the “random winding” type of winding, by changing the traversing speed at which the thread is wound onto the bobbin. Each workstation has a single motor drive activated for the rotation of the cross-wound bobbin, and a single motor drive activated for a traversing thread guide. The diameters (D SP k ) of the bobbin ( 8 ) which are critical with regarding to the development of ribbon windings depending on the width (B Sp ) of the bobbin ( 8 ) and a cross-winding angle (α) are determined, and, shortly before reaching each critical diameter (D SP k ), the cross-winding angle (α) is changed to a value (α 1 ), which avoids development of ribbon windings in this diameter region, and the cross-winding angle (α 1 ) is reset to its original value (α) after the critical diameter (D SP k ) has been passed.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of German patent application 10 2005054 356.1, filed Nov. 15, 2005, herein incorporated by reference.]

BACKGROUND OF THE INVENTION

The invention relates to a method for avoiding ribbon windings duringthe production of take-up bobbins Method for avoiding ribbon windings inthe production of take-up bobbins which are wound at the workstations oftextile machines producing cross-wound bobbins in the “random winding”type of winding, by changing the traversing speed at which the thread iswound onto the take-up bobbin, the workstations in each case having asingle motor drive, which can be activated in a defined manner for therotation of the cross-wound bobbin, and a single motor drive which canbe activated in a defined manner for a traversing thread guide.

During the production of take-up bobbins at workstations of textilemachines producing cross-wound bobbins, a thread which is manufacturedin an open-end spinning device, for example, and supplied at a virtuallyconstant speed to a winding device when running onto a bobbin isdisplaced by a traversing thread guide in such a way that it runs incrossing layers onto the bobbin and thus forms a so-called cross-woundbobbin. During the production of cross-wound bobbins in the “randomwinding” type of winding, there is, however, the problem that if noparticular measures are taken, so-called ribbon windings repeatedlyoccur in the course of the bobbin travel. Such ribbon windings alwaysoccur if a whole-number winding ratio is present, in other words, if thecross-wound bobbin carries out one or more complete revolutions perdouble stroke of the traversing thread guide. In a case such as this,the reversal points of the thread are substantially located over thereversal points of the previous stroke, so the thread is repeatedlyplaced on the same or a directly adjacent point on the winding peripherywhich leads to ribbon-like thread layers which are designated ribbonwindings.

As the stripping-off of complete yarn layers from the bobbin surfaceoften occurs when there is such a non-homogeneous structure of the yarnlayers when unwinding the cross-wound bobbins, and this leads to seriousoperating disruptions, ribbon windings of this type absolutely have tobe avoided.

Various methods and devices which are to be used during the bobbinbuild-up to overcome the aforementioned problems have therefore beenknown for a long time to avoid ribbon windings. With these so-calledribbon disrupting methods and mechanisms, the winding ratio isinfluenced in the regions of the cross-wound bobbin at risk of ribbonwinding.

DE 25 34 239 C2, for example, describes a device and a method for ribbondisruption, in which it is attempted, by means of constant changing ofthe cross-winding angle, to prevent the development of whole-numberwinding ratios. The traversing thread guides of one machine side can bedriven here together by a first drive at least two different speeds andthe winding rollers of this machine side can be driven together by asecond drive. The two drives are also connected to one another by anelectronic gearing in such a way that the winding rollers and thereforethe cross-wound bobbins are driven in such a way, synchronously and as afunction of the movement of the traversing thread guides, that thequotient of the rotational speed of the cross-wound bobbins and thecosine of half the thread cross-winding angle is constant.

In other words, in this known method, an attempt is made both to avoidwhole-number winding ratios and also to keep the resulting winding speedof the thread and therefore the thread tension virtually constant.

A ribbon disruption method is also known from DE 43 37 891 A1, in whicha thread supplied at a constant speed and wound onto a cross-woundbobbin in the “random winding” type of winding is wound on at achangeable traversing speed to avoid ribbon windings. The mechanism hasa single motor driven winding roller and a single motor driventraversing thread guide. In this known ribbon disrupting method, thetraversing speed of the thread guide is subjected to a non-periodicchange. The maximum and minimum values of the traversing speed, at whichin each case a changeover takes place from an acceleration to adeceleration and vice versa, and the time intervals between the reversalpoints, are changed in this case by means of a computer withinpredetermined limits.

A ribbon disrupting method is furthermore known from DE 196 28 402 A1,in which, similarly to in the mechanism according to DE 25 34 239 C2,the winding rollers of one machine side are driven together by a firstdrive and the thread guides of this machine side are driven together bya further drive.

The traversing speed of the thread guides and the rotational speed ofthe winding rollers are constantly changed here in opposite directionsbetween predetermined top and bottom values around an average value.

One of the two speeds in this case forms the reference variable whichthe other speed is made to follow as a following variable of the method.In each case, if the reference variable has reached a top or bottomvalue, at the beginning of its change in the opposite direction a signalis generated which triggers the change of the following variable in theopposite direction.

A ribbon disrupting method for cross-wound bobbins, which are wound inthe “random winding” type of winding, is also described in DE 102 09 851A1. In this known method, as a function of the delivery speed of thethread, the degree of tensioning drawing and the cross-winding angle,the rotational speed of the winding roller is fixed and thecross-winding angle is changed by changing the speed of the traversingthread guide for the purpose of ribbon disruption. The drive for thewinding rollers and the drive for the traversing thread guides areconfigured as speed-controllable motors, to which a signal representingthe value of the desired cross-winding angle is supplied, from which themotors derive the required motor speed.

The aforementioned ribbon disrupting methods or ribbon disruptingmechanisms have the disadvantage, however, that they are all relativelycomplicated or expensive.

In other words, to carry out the known methods, either a high mechanicaland control outlay is required or the ribbon disrupting methods lead tounsatisfactory results during the winding of the cross-wound bobbins.

SUMMARY OF THE INVENTION

Proceeding from the aforementioned prior art, the invention is based onthe object of providing a relatively simple method for avoiding ribbonwindings, which method is advantageous to use in particular inworkstations, which have single motor drives for the winding rollers andthe traversing thread guide.

This object is achieved according to the invention by a method asdescribed in claim 1. Method for avoiding ribbon windings in theproduction of take-up bobbins which are wound at the workstations oftextile machines producing cross-wound bobbins in the “random winding”type of winding, by changing the traversing speed at which the thread iswound onto the take-up bobbin, the workstations in each case having asingle motor drive, which can be activated in a defined manner for therotation of the cross-wound bobbin, and a single motor drive which canbe activated in a defined manner for a traversing thread guide,characterised in that the diameters (D_(SP k)) of the cross-wound bobbin(8) which are particularly critical with regarding to the development ofribbon windings and depend on the width (B_(Sp)) of the cross-woundbobbin (8) and a cross-winding angle (α) selected during the winding ofthe cross-wound bobbin (8), are determined, in that, in each case,shortly before reaching one of these critical diameters (D_(SP k)), thecross-winding angle (α) is changed to a value (α₁), which rules out thedevelopment of ribbon windings in this diameter region and in that thecross-winding angle (α₁) is reset again to its original value (α) afterthe critical diameter (D_(SP k)) has been passed.

Advantageous configurations of the invention are the subject of thesub-claims.

The method according to the invention offers the possibility of reliablypreventing right from the start the production of ribbon windings inthat suitable measures are already taken to disrupt ribbons before acritical region is reached during the winding of a cross-wound bobbin.In other words, shortly before reaching a critical region of this typepredetermined by the bobbin width and the cross-winding angle, thewinding ratio is adjusted in a defined manner by changing thecross-winding angle in such a way that the production of ribbon windingsare reliably ruled out. The changed cross-winding angle is retained hereuntil the critical diameter region of the cross-wound bobbin has beenpassed. The original cross-winding angle is then reset and windingcontinues with this cross-winding angle until in the course of thebobbin travel, the diameter of the cross-wound bobbin approaches thenext critical diameter region.

As shown in claim 2, the critical diameter regions of a cross-woundbobbin wound by the “random winding” type of winding is advantageouslycalculated by the formula: D_(SP k)=A×B_(SP)/π×tan(α/2), whereinD_(SP k) stands for a critical diameter region of the cross-woundbobbin, A stands for a whole number, B_(SP) stands for the respectivebobbin width of the cross-wound bobbin and a stands for the selectedcross-winding angle of the cross-wound bobbin. The diameter data can becalculated, for example, in a workstation computer and processed suchthat before a critical diameter region of the cross-wound bobbin isreached, a change in the cross-winding angle is in each case initiatedin a timely manner. The regions of the cross-wound bobbin are called acritical diameter region, in which a whole-number winding ratio ispresent, in other words, in which the cross-wound bobbin carries out oneor more complete revolutions per double stroke of the traversing threadguide because of the present diameter.

As described in claim 3, it is provided, in this case, in anadvantageous embodiment that the cross-winding angle is reduced shortlybefore reaching a critical cross-wound bobbin diameter, by reducing thespeed of the traversing thread guide.

The reduction in the cross-winding angle leads directly to a change inthe winding ratio with the result that ribbon windings cannot occur inthis per se critical diameter region of the cross-wound bobbin.

As shown in claim 4, to change the cross-winding angle, the workstationcomputer preferably initiates a speed change of the traversing threadguide. At the same time, the rotational speed of the winding roller andtherefore the winding speed of the cross-wound bobbin are also adjustedin such a way that the thread tension of the running-on threads remainsvirtually constant. In other words, the speeds of the traversing threadguide and winding roller are adjusted in such a way that the resultantforce of the displacement speed of the traversing thread guide and therotational speed of the winding roller constantly remain virtually thesame.

According to claim 5, the drive of the traversing thread guide ispreferably configured as a stepping motor. Such stepping motors areeconomical mass produced components, which can also be very preciselyactivated in a relatively simple manner. In other words, very precisedisplacement of the traversing thread guide is possible, for example,with such stepping motors, the outlay for control being kept withinreasonable limits.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention described in more detail below with the aid of anembodiment shown in the drawings, in which:

FIG. 1 shows a side view of a workstation of an open-end rotor spinningmachine producing cross-wound bobbins, with a winding device whichoperates by the method according to the invention,

FIG. 2 schematically shows, to an enlarged scale, the winding devicerequired to carry out the method according to the invention,

FIG. 3 shows a graph, which makes clear the connection between therotational speed of the winding roller and the speed of the traversingthread guide, in particular when there is a change in the cross-windingangle,

FIG. 4 schematically shows the thread run in a cross-wound bobbin, whichhas reached a critical diameter region.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a side view of one half of a textile machine1 producing cross-wound bobbins, in the embodiment of an open-end rotorspinning machine. Textile machines of this type, as known, have betweentheir end frames (not shown) a large number of similar workstations 2,which inter alia have a spinning unit 3, in each case, as well as awinding device 4. Fibre bands 6, which are stored in spinning cans 5,are processed to form threads 7 in spinning units 3, which threads arethen wound on the winding devices 4 to form cross-wound bobbins. Thefinished cross-wound bobbins 8 are conveyed, for example, by means of across-wound bobbin transporting mechanism 12 to a loading station (notshown) arranged at the end of the machine.

As also indicated in FIG. 1, the individual workstations 2, apart fromthe spinning unit 3 and the winding device 4, also have further handlingmechanism, for example a thread take-off mechanism 10, a suction nozzle17 or a waxing device 14. The functions of these components are knownand described in detail in numerous patents.

The winding device 4 substantially has a creel 9, a winding roller 11 aswell as a thread traversing mechanism 16. The winding roller 11, whichcan be driven by a single motor by means of a drive 13, in this casedrives the cross-wound bobbin 8, which is freely mounted in the creel 9,by frictional engagement.

FIG. 2 schematically shows a front view of a winding device 4 requiredto carry out the method according to the invention.

As indicated in the drawing, the cross-wound bobbin 8 freely rotatablyheld in a creel (not shown) rests on a winding roller 11 and isentrained thereby by frictional engagement.

The winding roller 11 is in this case connected to a drive 13, which isin turn connected via a control line 23 to a workstation computer 19. Todisplace the thread 7 while running onto the bobbin 8, a threadtraversing mechanism 16 is also provided, the traversing thread guide 18of which is driven in an oscillating manner by its own drive, preferablya stepping motor 20. The stepping motor 20 is also connected to theworkstation computer 19 via a control line 24 and can be activatedthereby in a defined manner.

Furthermore, a sensor mechanism 21 is provided, which is connected via asignal line 22 to the workstation computer 19 and detects the respectiverotational speed of the cross-wound bobbin 8 during the winding process.In other words, the workstation computer 19 is supplied with signals ofthe sensor mechanism 21 and, using the rotational speed of the windingroller, the known diameter of the winding roller and the rotationalspeed of the cross-wound bobbin 8 determined by the sensor mechanism 21constantly calculates the instantaneous diameter of the cross-woundbobbin 8.

FIG. 3 shows a graph, in which the speed V_(FF) of the traversing threadguide 18 is shown on the abscissa and the rotational speed V_(WW) of thewinding roller 11 is shown on the ordinate. As indicated, a threadtake-up speed V_(A1) is produced during the regular bobbin travel at aspeed V_(1 FF) of the thread guide 18 and a rotational speed V_(1 WW) ofthe winding roller 11. In this case, the thread runs onto thecross-wound bobbin 8 at an angle α/2.

Shortly before reaching a critical diameter region D_(SP k) of thecross-wound bobbin 8, the value of the thread run-on angle α/2 ischanged to α₁/2. In other words, the speed of the thread guide 18 isreduced to V₂ FF, as shown in FIG. 3. In order to keep the threadtake-up speed V_(A1)=V_(A2) constant, the rotational speed of thewinding roller 11 is also adjusted in such a way that the winding roller11 now rotates at V_(2 WW). This means that the resulting thread take-upspeed V_(A1) or V_(A2) being produced from the rotational speed V_(WW)of the winding roller 11 and the speed V_(FF) Of the thread guide 18remains constant regardless of the thread cross-winding angle α or α₁.

FIG. 4 shows a cross-wound bobbin 8, which has reached a first criticaldiameter region D_(SP k) depending on the bobbin width B_(SP) and thecross-winding angle α. As indicated with the aid of the line 30representing the thread run, or the associated arrows 31 to 36, aplurality of complete revolutions of the cross-wound bobbin 8 would takeplace at this diameter of the cross-wound bobbin 8 and a cross-windingangle α per double stroke of the traversing thread guide 18, with theresult that the thread would be placed in thread deposits located oneabove the other.

In order to avoid ribbon windings, the value of the cross-winding angleα is changed to α₁ shortly before reaching the critical diameter regionD_(SP k). At a cross-winding angle α₁ and a bobbin width B_(SP), it isensured, in the region of the cross-wound bobbin diameter D_(SP k) thatno ribbon windings can occur.

The thread run being adjusted at a cross-winding angle α₁ and a bobbinwidth B_(SP) is indicated in FIG. 4 with the aid of the line 40 or theassociated arrows 41 to 49.

Functioning of the method according to the invention:

At the beginning of a batch, firstly the most important parameters ofthe cross-wound bobbin, for example the provided final diameter of thecross-wound bobbin 8, the bobbin width B_(SP), the cross-winding angleα, with which the cross-wound bobbin 8 is to be wound, as well as afurther cross-winding angle α₁ are established and input for exampleinto the central control unit of a textile machine.

The central control unit of a textile machine is, in this case, in turnconnected to the individual workstation computers 19 of the workstations2 preferably via a bus connection or the like. The central control unitor the workstation computers 19 firstly calculates/calculate, with theaid of the aforementioned data, the critical diameter regions D_(SP k)of the cross-wound bobbin, in other words, the regions in which if noparticular measures are taken, ribbon windings would occur. For example,the workstation computer 19 determines with the aid of the formula:D_(SP k)=whole number x bobbin width B_(SP)/π×tan cross-winding angleα/2, that at a bobbin width of, for example, 150 mm and a cross-windingangle of α=36°, the particularly critical diameter regions of thecross-wound bobbin 8 are at D_(SP k)=147 mm, 294 mm etc.

After the start of the spinning/winding process the rotational speed ofthe cross-wound bobbin 8 is constantly monitored by means of the sensormechanism 21 and the current diameter D_(SP) of the cross-wound bobbin 8is constantly calculated in the workstation computer 19 according to theformula: D_(SP)=D_(WW)×n_(ww)/n_(SP).

If the workstation computer 19 establishes that the diameter D_(SP) ofthe cross-wound bobbin 8 is approaching a critical diameter regionD_(SP k), the value of the cross-winding angle α is changed to α₁, forexample reduced from α=36° to α₁=30°. The reduction in the cross-windingangle α to α₁ takes place here by reducing the speed V_(FF) of thetraversing thread guide 18. In other words, the workstation computer 19activates the drive 20 of the thread traversing mechanism 16 in thedirection of “deceleration”.

In order to continue to keep the thread tension of the thread 7 runningonto the cross-wound bobbin 8 constant, the workstation computer 19simultaneously also activates the drive 13 of the winding roller 11 inthe direction of “acceleration”. In other words, the rotational speedV_(WW) of the winding roller 11 is increased in such a way that thetake-up speed V_(A) of the thread 7 onto the cross-wound bobbin 8remains virtually constant despite the change in the cross-windingangle.

The invention is not limited to the embodiment shown; in an alternativeembodiment, instead of the workstation computers, section computers orthe central control mechanism of the textile machine can obviously alsobe used as the control computer.

1. Method for avoiding ribbon windings in the production of take-upbobbins which are wound at the workstations of textile machinesproducing cross-wound bobbins in the “random winding” type of winding,by changing the traversing speed at which the yarn is wound onto thetake-up bobbin, the workstations in each case having a single motordrive, which can be activated in a defined manner for the rotation ofthe cross-wound bobbin, and a single motor drive which can be activatedin a defined manner for a traversing yarn guide, characterised in thatthe diameters (D_(SP k)) of the cross-wound bobbin (8) which areparticularly critical with regarding to the development of ribbonwindings and depend on the width (B_(Sp)) of the cross-wound bobbin (8)and a cross-winding angle (α) selected during the winding of thecross-wound bobbin (8), are determined, in that, in each case, shortlybefore reaching one of these critical diameters (D_(SP k)), thecross-winding angle (α) is changed to a value (α₁), which rules out thedevelopment of ribbon windings in this diameter region and in that thecross-winding angle (α₁) is reset again to its original value (α) afterthe critical diameter (D_(SP k)) has been passed.
 2. Method according toclaim 1, characterised in that the critical diameters (D_(SP k)) of thecross-wound bobbin (8) are determined according to the formula(D_(SP k))=(whole number) x bobbin width (B_(Sp))/π×tan of half thecross-winding angle (α/2).
 3. Method according to claim 1, characterisedin that the cross-winding angle (α) is reduced shortly before reaching acritical diameter (D_(SP k)) of the cross-wound bobbin (8).
 4. Methodaccording to claim 1, characterised in that to change the cross-windingangle (α), the speed (V_(FF)) of the traversing yarn guide (18) ischanged, the rotational speed (V_(WW)) of the winding roller (19) beingsimultaneously adjusted in such a way that the yarn tension of therunning-on yarn (7) remains virtually constant.
 5. Method according toclaim 4, characterised in that a stepping motor (20) is used as thedrive for the traversing yarn guide (18).